1. Field of the Invention
This invention relates to a process for recycling of polymeric materials, in particular rubber and elastomers, in which the polymeric material is pulverized in a manner which does not change its chemical composition so as to produce a polymeric powder, which polymeric powder is then reformed into a single piece of polymeric material. The process of this invention reconstitutes the polymeric material, such as rubber, without changing its chemical structure whereby chemical bonds that were broken during the pulverization process are linked.
2. Description of Prior Art
Present devulcanization and thermomechanical processes for reconstitution of rubber change the chemical structure of the rubber and, in turn, reproduce rubbers having poorer mechanical properties than the original rubber. Processes for the reconstitution of rubber are taught, for example, by U.S. Pat. No. 4,665,101 which teaches a method for the continuous, dry, non-pressurized regeneration of salvaged rubber in which the rubber is heated to a reclamation temperature in a two-stage process, whereby the overall heat required is introduced by microwave heating and conventional heating; U.S. Pat. No. 4,851,500 which teaches a process and apparatus for making a rubber-like product from rubber scrap in which the rubber scrap is mixed with added sulphur and a pressure of about 1,000 to 3,000 pounds per square inch applied thereto for one to ten minutes at a temperature of about 250.degree. to about 450.degree. F.; U.S. Pat. No. 5,578,700 which teaches a method and apparatus for recovering devulcanized rubber or purified carbon and volatiles from a crumb rubber feed material in which the material is introduced into a first chamber under pressure, the pressure is reduced and the rubber particles are conveyed therethrough with a screw conveyor, microwave energy input is provided to the rubber particles so as not to effect chemical destruction of volatile components, the volatiles are recovered from the rubber particles after it has been heated, and rubber crumb is withdrawn from the first chamber, which steps are then repeated in a second chamber; U.S. Pat. No. 5,527,409 which teaches a method of making recycled tire roof sheeting in which used tires are shredded into small particle sizes and subsequently compacted into large log-like articles; U.S. Pat. No. 4,506,034 which teaches a method for continuously processing coarse-grain waste rubber into a secondary rubber raw material in which the coarse-grain waste rubber is exposed to a thermoshock without access to oxygen at a temperature of about 200.degree. C. to 900.degree. C. for a period of 5 to 200 seconds; and U.S. Pat. No. 4,469,817 which teaches the reclamation of vulcanized rubber by heating powdered vulcanized rubber to a temperature for desulpherization of the rubber and, on completion of the desulpherization, cooling the desulpherized rubber to a temperature at which substantially no oxidation thereof can occur.
Numerous methods for breaking down rubber compounds for recycling and other applications are well known to those skilled in the art. U.S. Pat. No. 4,607,796 teaches a method for producing powders from rubber and vulcanization products in which the source material is pulverized in an extruder in which it is first compressed by a force of 0.2 to 0.7 MPa and then subjected simultaneously to a pressure ranging from 0.2 to 50 MPa at a sheer force ranging from 0.3 to 5N/mm.sup.2 while heating the material to a temperature ranging from 80.degree. C. to 250.degree. C. and then cooling the material to a temperature ranging from 15.degree. C. to 60.degree. C. U.S. Pat. No. 5,258,413 teaches a continuous ultrasonic method for breaking the carbon-sulphur, sulphur-sulphur, and carbon-carbon bonds in a vulcanized elastomer. U.S. Pat. No. 5,411,216 teaches a shredding machine and process for recycling used vehicular tires comprising a primary shredder and process, a secondary shredder and process, a granulator and a first process, a material separating means and process, and a granulator and a second process. Finally, U.S. Pat. No. 4,499,218 teaches a vulcanizable rubber compound comprising an oxidized oligomer derived from thermally decomposed rubber materials, and containing a diene rubber.